Proteins derived from soybean have a well amino acid balance, and in recent years, physical effects such as an action of decrease in serum cholesterol have been reported. In order to decrease risks of increased cholesterol and cardiac diseases, the U.S. Food and Drug Administration (FDA) recommends ingesting 25 g (6.25 g per serving) or more of a high quality soybean protein in diet for one person per day. Also in Japan, food having a function of lowering serum cholesterol, which contains 6 g or more of soybean globulin for one person per day, has been approved as specified health food.
Soybean protein can be generally ingested from traditional soybean products such as soybean milk, soybean curd, and natto (fermented soybeans). In recent years, in bakery products such as bread and baked goods, beverage or gelled nutrition-balanced foods, and the like, foods added with a soybean protein isolate or soybean protein products such as soybean powder, soybean milk, soybean milk powder, and the like have been largely commercially available and become popular.
However, a general soybean protein isolate used in the food industrial field is subjected to a high temperature and high pressure treatment for sterilization and giving physical properties, and thus heat denaturation is caused. In the case of adding this soybean protein isolate to a dough added with wheat flour or gluten in a low moisture system, since binding capacity is lacking in the soybean protein isolate, the dough easily breaks because of low binding capacity, and the noodle becomes sodden and has texture without toughness after boiling. When an amount of incorporated soybean protein isolate is large, a noodle strip with normal quality can not be obtained and noodle-making properties are poor, and when an obtained noodle is boiled, the noodle breaks in pieces, and thus, a good shape of noodle can not be formed. When an amount of incorporated soybean protein isolate is small, noodle making is possible, but workability and texture tend to deteriorate.
Further, in soybean-based materials such as soybean powder, defatted soybean, and concentrated soybean protein (acid concentrate, alcohol concentrate) containing a large amount of a bean curd refuse component, noodle-making properties are inhibited by fibers derived from the bean curd refuse. Further, when an obtained noodle is boiled, the noodle is sodden and easily breaks in pieces and its texture and taste are also very poor. Improvement methods of physical properties of noodle, using a soybean powder in Patent Documents 1 and 2, using an insoluble soybean protein in Patent document 3 and using soybean milk in Patent Document 4, are disclosed. However, in any of these disclosures, an amount of soybean protein is not more than 5% by weight in a noodle solid content, and a nutritious effect of soybean protein can not be expected. Patent Document 5 describes that a soybean protein isolate can be added up to 30% by weight (23% by weight in a solid content) based on wheat flour in noodle materials by treatment of protein degradation and powderization of O/W emulsion. However, physical properties of obtained dough and noodle can not be considered to be sufficient. Further, adding a larger amount of it can not be applied.
On the other hand, patients with food allergy have been rapidly increased in recent years, and in particular, allergy to grain that is a staple food is serious. Wheat is one of these allergens, and a patient with wheat allergy causes allergic symptoms such as rash, dyspnea, and diarrhea by wheat ingestion. When a patient with celiac syndrome ingests a gluten-containing food, the immune system is reacted because of having no resistance to gluten protein contained in wheat, and inner membrane of the small intestine is damaged to cause nutrient malabsorption.
For such a patient without having resistance to wheat, a food from which wheat, particularly gluten, is removed is necessary, and in Patent Document 6, wheat flour in which gluten is degraded with an enzyme is proposed. However, processing is difficult since gluten is not present, and produced food also has poor texture.    Patent Document 1: JP 54-70446 A    Patent Document 2: JP 54-84048 A    Patent Document 3: JP 56-45168 A    Patent Document 4: JP 55-165773 A    Patent Document 5: JP 60-137256 A    Patent Document 6: JP 9-172995 A